接近開關(guān)類型有NPN型和PNP型兩種，對于PNP型的接近開關(guān)它的輸出信號是高電平有效，也就是說當(dāng)有檢測物體靠近它時(shí)，其信號輸出端就會(huì)有輸出一個(gè)高電平；當(dāng)檢測物體遠(yuǎn)離接近開關(guān)時(shí)，它的信號輸出端就會(huì)恢復(fù)到低電平。而對于NPN型接近開關(guān)它的輸出信號是低電平有效，因此我們就知道，我們平時(shí)所用的接近開關(guān)是屬于開關(guān)型的，也就是說接近開關(guān)在工作時(shí)要么輸出的是高電平，要么輸出的是低電平。
用萬用表檢測接近開關(guān)主要是檢測它在電路工作中所輸出的電壓信號；另一種是在斷電情況下測量接近開關(guān)信號輸出端和電源接線端的阻值情況。我們常用的接近開關(guān)一般分為NPN型的和PNP型的，因此用萬用表檢測它的輸出電壓時(shí)要注意分清楚接近開關(guān)的三根線的性質(zhì)，我們常見接近開關(guān)有三根線，它們分別是棕色線、藍(lán)色線和黑色線，其中棕色線接直流24V電源正極；藍(lán)色線接24V電源負(fù)極；黑色線是接近開關(guān)信號輸出線。

There are two types of proximity switches: NPN type and PNP type. For PNP type proximity switches, the output signal is effective at a high level, which means that when a detected object approaches it, the signal output terminal will output a high level; When the detected object moves away from the proximity switch, its signal output will return to a low level. For the NPN type proximity switch, its output signal is effective at low levels. Therefore, we know that the proximity switch we usually use belongs to the switch type, which means that the proximity switch either outputs a high level or a low level during operation.
Using a multimeter to detect proximity switches is mainly to detect the voltage signal it outputs during circuit operation; Another method is to measure the resistance between the output terminal of the proximity switch signal and the power supply terminal in the event of a power outage. The proximity switches we commonly use are generally divided into NPN type and PNP type. Therefore, when using a multimeter to test its output voltage, it is important to distinguish the properties of the three wires of the proximity switch. We commonly see three wires of the proximity switch, which are brown wire, blue wire, and black wire, with the brown wire connected to the positive pole of the DC 24V power supply; Connect the blue wire to the negative pole of the 24V power supply; The black line is the output line of the proximity switch signal.